1. Field of the Invention
The present invention relates to a structure, as well as its manufacturing method, formed three-dimensionally by using MEMS (Micro Electro Mechanical Systems) technology or NEMS (Nano Electro Mechanical Systems) technology. In particular, the invention relates to a three-dimensional structure, as well as its manufacturing method, in which micro three-dimensional structure elements having a movable structure are arranged in an elastic body.
2. Description of the Related Art
In the research and development of robot technology, it is one of important issues how an object is reliably controlled by a robot hand. More specifically, with respect to an operation of grasping an object by a robot hand, not only detecting grasping force to grasp the object therewith but also detecting a shearing stress occurring to the hand surface due to the grasping operation is needed for reliable control of robot hands. The reason of this is that detecting a frictional force generated between the object and the hand surface by the shearing stress lends it exerting optimum frictional-force control to fulfill reliable control of the object.
In recent years, tactile sensors aimed at detecting such shearing stress have been being developed. See, e.g., Kentaro Noda, Kazunori Hoshino, Kiyoshi Matsumoto, Isao Shimoyama, “300 nm-thick cantilevers in PDMS for tactile sensing”, Proc. IEEE MEMS'05, pp. 283-286, 2005. An example of such conventional tactile sensors is explained below with reference to a schematic perspective view shown in FIG. 19.
As shown in FIG. 19, a tactile sensor 501 includes a plurality of piezoresistive cantilevers 502, which are cantilevers with piezoresistors on its hinges, formed from a thin film of about several hundred nanometers, one sheet of substrate member 503 on which those cantilevers 502 are fixed at its top face, and a film-like elastic body 504 which is placed inside the substrate member 503 so as to allow the cantilevers, which are fixed on the top face of the substrate member 503, to be embedded therein.
Each of the cantilevers 502 has one end formed as a fixation portion for the substrate member 503 and the other end formed as a movable portion which is movable only in a thicknesswise direction of the thin film that forms the cantilever 502. The individual cantilevers 502 are electrically connected to an unshown control unit through unshown terminal portions and wiring. For example, upon occurrence of a shearing stress in the film-like elastic body 504, the shearing stress causes the movable portion of the cantilever 502 to be activated and deformed, thus making possible to detect the shearing stress. In each of the cantilevers 502, a piezoresistive portion for detecting any deformation of the movable portion is formed. Further, in order to detect shearing stresses of various directions acting on the film-like elastic body 504, the cantilevers 502 are arranged within the film-like elastic body 504, as it is fixed on the substrate member 503, so that their movable portions are differed in movable direction, for example, that their movable directions are set along X-axis, Y-axis and Z-axis directions as shown in the figure.
With the tactile sensor 501 constructed as shown above, contact of the film-like elastic body 504 with an object or the like makes it possible to detect shearing stresses in various directions occurring within the film-like elastic body 504 by the cantilevers 502, respectively. It is noted that such a film-like elastic body 504 is formed from, for example, PDMS (polydimethylsiloxane), which is a material that is easily elastically deformed by application of external force. The substrate member 503 is given by using SOI wafer, which is formed of Si or SiO2.